


must be something

by knave_of_swords



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Alpha/Beta/Omega Dynamics, Anal Sex, Cuddlefucking, F/F, FE3H Omegirlverse Week, Fire Emblem: Three Houses Black Eagles Route, Knotting, Mating Cycles/In Heat, Pre-Timeskip | Academy Phase (Fire Emblem: Three Houses), Smut, Vaginal Sex
Language: English
Status: Completed
Published: 2021-02-12
Updated: 2021-02-12
Packaged: 2021-03-18 11:53:56
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,361
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29368071
Author URL: https://archiveofourown.org/users/knave_of_swords/pseuds/knave_of_swords
Summary: Crests have certain side effects for their bearers in addition to the power they bestow. Whoever bears a crest bears that crest's presentation as either an alpha or an omega. When the Crest of Flames (omega) is forced on Edelgard, who already bears the Crest of Seiros (alpha), her presentation becomes... complicated. She's able to keep it a secret, until she goes into a rare and inconveniently timed heat. Luckily for Edelgard, Lysithea is uniquely qualified to both understand her situation and help her out (by railing her into the mattress).
Relationships: Edelgard von Hresvelg/Lysithea von Ordelia
Comments: 1
Kudos: 29
Collections: Horny Void





	must be something

**Author's Note:**

> cntw only because lysithea is technically underage, but i dont like to stick underage on as a warning unless i'm kinking on it, which this isn't

Edelgard is in the desparate haze of a heat, and that's probably why she doesn't think twice before opening her door for Hubert when she hears him knock.

"What the hell? I thought you were an alpha. The Crest of Seiros is an alpha crest." Lysithea stands in front of her door, where Hubert should be, her eyes narrowed and her arms folded in front of her.

Edelgard can't keep her door open like this, the scent of her heat leaking out, but she also can't just ignore Lysithea now. So Edelgard grabs Lysithea's arm and pulls her inside her room, slamming the door shut behind her.

"Seriously, Edelgard. What the hell? You've smelled like an alpha all year, but right now you smell like you're in heat." Lysithea covers her nose and mouth with the end of her sleeve. "Wait--" Lysithea's eyes widen. "You did undergo a blood reconstruction surgery like I did. Somehow, those mages got to you too and gave you a second crest, an omega crest!" Lysithea looks triumphantly at Edelgard. Her eyes are shining, and Edelgard finds herself momentarily entranced. "I was right!"

Edelgard squeezes her eyes shut, thrown out of her heat-induced reverie. Lysithea knows that she has two crests. This could screw up all of her plans. Years of painstaking planning, countless deaths, and so many concessions made to her uncle, all undone because Edelgard couldn't keep her damn scent under control.

"You can't tell anyone," she finally says. "Please, Lysithea." Edelgard opens her eyes again to look at Lysithea. The triumphant look on her face fades a little, growing concern replacing it. Edelgard wonders if Lysithea always looks this lovely. She smells nice, too. There's a hint of perfume in there-- a flowery sort of scent Edelgard vaguely recalls smelling on Hilda before, but it suits Lysithea so much better.

"I--" Lysithea hesitates. "I have questions, but it's not like I want people to know about my second crest either. I won't tell anyone." The tense knot tied in Edelgard's stomach loosens a little. "You need to do something about your scent, though." The tension in her stomach returns.

"I know," Edelgard snaps. "I don't know how to control the omega scent thing when it goes out of control like this. It normally isn't an issue because of my Crest of Seiros, but this time it isn't enough." Clearly. She can already see Lysithea becoming distracted, blinking more than normal to try and help her focus. "Setting aside the fact that I shouldn't be an omega, I am not going to be bred in public."

It could be possible, to explain how she's in heat. Very rarely, a crest-bearer would have an inverted orientation from what the crest should give them. Lorenz even has the condition, but he's the only one currently known of in Fodlan and has been for at least a generation. Edelgard could claim a situation like that, explaining her previous alpha presentation as the result of extreme suppressants meant to present a strong heir to the Empire.

That wouldn't save her from a public breeding, of course. It would nearly certainly make the experience worse for her, actually. Omegas who can't control themselves in public are embarrassing and in need of some discipline to ensure better behavior in the future. Omegas who hide their orientation and pretend to be a beta or an alpha are shameful, and need to be punished for their sin. What would be an undignified, but routine, affair for any other omega would become a thoroughly humiliating public scandal for her at the hands of Seteth or Rhea.

"You don't have much time before we're supposed to go rout bandits with the rest of the Black Eagles," Lysithea says, snapping Edelgard out of her thoughts. She's chewing her lip, eyebrows furrowed the same way as when she spars with the professor with a sword. Hesitant, concerned, calculating. She clearly has more she wants to say, so Edelgard just nods, hoping that the silence will pull whatever Lysithea is holding back out of her mouth. She focuses on watching Lysithea's mouth as she bites her lip.

"I can help you," Lysithea finally says after a long pause. "If you want. Charon and Gloucester are both alpha crests. I haven't--" Lysithea stops herself. "I could do it. Help you with this."

Everything in Edelgard's body begs her to say yes, but she still hesitates for a moment. It had been a long time since she was last in heat. She doesn't know how to be an omega, mate like an omega. But Lysithea is right, and this is clearly the best solution. At least Edelgard trusts Lysithea. Not as much as Hubert, but a beta could only do so much to alleviate an omega's or alpha's needs.

"That is acceptable," Edelgard says, unbuttoning her shorts and shoving them down her legs before she loses her nerve. "I'll be counting on you, Lysithea."

Lysithea is on her in an instant, face pressed into the crook of Edelgard's neck and hands eagerly grabbing at her hips to pull her closer. Edelgard staggers backwards at the impact but manages to keep herself from falling. At least, until Lysithea's scent hits her. They've barely started, and already Lysithea smells intoxicating, her scent as strong as when most other alphas would be about to climax.

"Are-- are you rutting?" Edelgard asks. Though she thinks she would have noticed, if Lysithea had been in rut, when she first came into her room. Lysithea pulls her head away from Edelgard's neck.

"No," Lysithea says curtly as Edelgard feels her whole body tense up for a moment. Then the tension releases. "I-- it's a side effect. Because both of my crests are alpha crests. I take some suppressants to help keep it under control, but--"

Edelgard cuts her off with a kiss. It had been a mistake of her to ask Lysithea a question, to pull her attention away from taking care of the burning need inside of her to be knotted.

Edelgard had initiated the kiss but it's Lysithea who takes charge, pushing her tongue against Edelgard's lips and into her mouth. She pushes Edelgard back until the backs of her knees hit her bed frame, causing her to collapse against the mattress. Lysithea doesn't break the kiss and instead falls down with Edelgard, letting her entire body lay on top of Edelgard.

Edelgard knows that Lysithea is physically incapable of subduing her. That she can carry Lysithea with ease, maybe with one hand if she has the help of her crest. It doesn't matter. Lysithea's face against her neck had made Edelgard weak in the knees; Lysithea's body on top of her has her lightheaded and breathless.

Lysithea is straddling her now, and Edelgard can feel the press of her erection against her, making her cunt throb with need. Edelgard breaks the kiss, intending to politely ask Lysithea to get on with it.

"Inside me," is what she manages to get out of her mouth, her mind in a hormonal haze. "Get inside me already."

Lysithea's mouth almost forms a smirk, but she promptly hooks her fingers around the top of Edelgard's tights-- when had she worked her way that close to Edelgard's skin?-- and yanks, so hard that Edelgard briefly wonders if she's ripping her tights. Not that she cares right now. Any other time, she would, but she desperately needs Lysithea inside her right now, everything else be damned.

It's amazing what the hormones of a heat can do to a person, Edelgard thinks as the cool air of the room brushes against her bare legs. She normally hates showing her bare skin, feeling most comfortable when in heavy armor that leaves her impervious to all but the most severe physical damage. Yet here she is, her skin burning underneath against her clothes, aching to press her bare skin against Lysithea. For Lysithea's mouth to be on her, everywhere, for her scent to flood Edelgard's body and flush this cursed heat out of her. Or maybe this heat is a blessing, because without it she never would have known how amazing Lysithea's scent could make her feel.

At least Lysithea is hiking up her skirt and yanking down her tights, meaning that-- Oh. Wow. Edelgard can't tell if it's just Lysithea's tiny frame making her cock seem bigger, or if it's really just that big, but either way, she needs it inside of her right now. 

She opens her legs and exposes her slick cunt to Lysithea, desparation making her shameless. Lysithea doesn't move quickly enough, so Edelgard hooks her legs around Lysithea and pulls her towards her. Her cock presses against Edelgard's lower stomach, and she can tell that it really is that big after all.

"Calm down!" Lysithea huffs at her. "I just wanted to look a bit." She pulls back, though only enough as she needs to press her cock against Edelgard's cunt. "Wow," she says, pushing a finger into Edelgard. "You're really wet." Lysithea takes her finger out of Edelgard, and adjusts her cock so that the head of it presses right at the outside of Edelgard's cunt. She bites her lip, hesitating.

"Lysithea," Edelgard says in a voice that's almost a whine. "Please." She tightens her legs around Lysithea's waist and pulls Lysithea closer, forcing the head of her cock inside of Edelgard. It's not nearly enough to fill her, but it does prod Lysithea to start moving. Her hands grab Edelgard's hips, adjusting the angle and holding her steady as she slowly pushes her cock into Edelgard. 

Lysithea starts to thrust back and forth, slowly at first, but then faster. Edelgard does her best to match Lysithea's rhythm, squeezing her legs around Lysithea's waist to pull her in deeper. It isn't long before Lysithea's pace gets more frantic, Edelgard starts to feel a coiled heat tighten in her core. An electric pulse shoots through her body when she feels the base of Lysithea's cock start to swell. She clenches down on Lysithea's cock, drawing out a whine from Lysithea. 

"Edelgard," Lysithea says with a gasp. She thrusts harder, deeper into Edelgard, until even the base of her inflating knot is inside Edelgard's cunt.

Lysithea's knot keeps expanding. Edelgard feels what she knows should be white hot pain at the entrance to her cunt, but she's so deep into her heat t hat the sensation registers only as throbbing pleasure. Lysithea's knot expands so far that Edelgard thinks she might actually break, until it finally stops and holds, and warmth fills Edelgard's cunt as Lysithea releases herself inside of her. 

Lysithea comes inside of her. Edelgard feels the warmth and knows what it means. The thought of Lysithea's come inside of her sends her shuddering through another orgasm, and she clenches hard around Lysithea's cock as it continues to spill and spill inside of her. 

When Lysithea is finally done, she slowly works her cock out of Edelgard and then leans back. They're both breathing hard, and the relief Edelgard should be feeling as her heat dissipates is replaced with something else-- a familiar arousal that couldn't have come at a more inconvenient time. Edelgard groans. 

"What's the matter?" Lysithea asks, apparently able to tell that this groan was not one of pleasure.

"I'm going into rut," Edelgard sighs. "Thank you for your help with my heat. I--"

Lysithea interrupts her, putting her hand on Edelgard's slowly stiffening cock and driving all words out of Edelgard's head. 

"Lysithea?"

Lysithea runs her hand down Edelgard's cock, and then back up, before answering.

"You know how both of my crests are alpha crests?" she says. Edelgard nods. Lysithea squeezes Edelgard's cock, making her bite her lip. She hopes Lysithea gets to her point quickly, while she can still think. "I usually need to come more than once, once I get going."

Edelgard waits for Lysithea to continue, but she doesn't.

"What are you getting at?" she asks.

"I'm saying that we could go again. If you want." 

Edelgard's cock throbs at the thought. 

"Again? How do you mean?" Edelgard knows what she hopes Lysithea means. She wonders if Lysithea's pussy would be too small for her cock or not.

"You do have another hole," Lysithea says instead, sending an unexpected thrill through Edelgard as she realizes what Lysithea is referring to. Her ass. She does have a hole there, but it doesn't seem like fucking it would help her through her rut. But it also probably wouldn't be terrible to let Lysithea have her ass. It's the least she could do for her after she helped Edelgard out with her heat, and she could at least hump the mattress while Lysithea takes her ass. And it's not like the thought of Lysithea fucking her there is entirely unappealing.

"Very well," Edelgard says, and turns herself over onto her stomach. When Lysithea pushes the head of her cock against her rim, Edelgard's muscles feel like they've turned to jelly. She had been holding herself up on her elbows, but her arms collapse and she gets a face full of her mattress. If she weren't so ridiculously horny, she would be embarrassed at the indignity. 

Edelgard doesn't realize that Lysithea is leaning over her back, pressing against her, until Lysithea grabs her shoulders. 

"Edelgard? Are you okay?" she asks. How sweet of her, Edelgard thinks distantly as her ass throbs around the tip of Lysithea's cock. 

"I'm fine," Edelgard says, though she's a bit muffled by the mattress. "Just fuck me already. Please."

Lysithea snorts, which isn't the reaction Edelgard had been expecting. 

"You must be so out of it if you're actually swearing. Is this what you're like behind that mask you pretend not to wear?"

"Lysithea, I swear--" Edelgard interrupts herself with a moan when Lysithea pushes deeper inside of her. Somehow Lysithea's cock feels even bigger now that it's in her ass.

Edelgard loses track of coherent thought when Lysithea starts to move, heat shooting through her body with every thrust going deeper inside of her ass. She doesn't know how long Lysithea fucks her as her dripping cock rubs against the mattress, but she feels another orgasm start to build inside of her. Is she really going to come from getting fucked in the ass while she's in rut?

Apparently the answer to that question is yes. Edelgard makes a strangled noise when the base of her cock starts to inflate. A knot. How ridiculous. Her cock isn't even inside anything. Yet her knot still inflates, desperate for touch. 

Her hands are somewhere beneath her, and Edelgard moves them to grab her cock, squeezing at the base where her knot is expanding. She feels like she's been wound to her breaking point. Any more and she's going to break, oh she's definitely going to break around Lysithea's cock and she's going to love every moment. 

It's when Lysithea's knot starts to inflate again, that Edelgard finally topples over the edge and climaxes. She knows how big that knot is. She knows how much it stretched her cunt, the knot that's about to obliterate her ass, and that knowledge has Edelgard coming, crying out as she sprays her seed across the sheets beneath her, the sticky fluid making a mess, smearing against her stomach as Lysithea continues to fuck her relentlessly. 

The stretch of Lysithea's knot around Edelgard's hole is even bigger than Edelgard expects. It feels incredible, and the knot is the only thing Edelgard can feel, until Lysithea comes inside of her again, filling her ass with come. 

It's a long moment, the sounds of both of them recovering their breath filling the silence, before either of them speak again.

"Do you need more?" Edelgard asks. She doesn't know if she could actually take more, but she wants to. She wants Lysithea to fuck her like that again. She wants Lysithea to put her cock back inside of her and never take it out except to switch holes. 

"I think I'm good," Lysithea says, breathing heavily. "Actually, I'm... exhausted." With that, Lysithea groans and flops onto Edelgard's mattress face-first. Unsurprising, if Edelgard's own sudden exhaustion is anything to go by.

A knock at Edelgard's door. She and Lysithea both jump. Edelgard wills her voice to be steady as she calls out.

"Who is it?"

"It's Hubert, lady Edelgard. Here to relay a message from the professor." 

Edelgard's eyes widen. She looks towards Lysithea, who looks similarly taken aback. They had both forgotten that they had somewhere else to be right now. Edelgard motions for Lysithea to stay where she is, covered up by her skirt and Edelgard's blankets. As an afterthought, Edelgard arranges her sheets so she's covered as well.

"I think you should step inside, Hubert," she says. Lysithea frowns at her, but doesn't say anything.

Hubert's eyes widen as soon as he steps inside the room. The smell of sex is strong even to betas, Edelgard remembers. 

"I believe I understand the situation," he says. Edelgard nods. "The timing of this is most fortuitous, as the professor asked me to notify you both that you two are exempt from today's outing."

"How convenient," Edelgard says with a frown. "Did they give a reason?" 

"They said that you were both overlevelled," Hubert answers. "I do not understand what that is supposed to mean, but it did not seem intended as a slight." Well, whatever that means, Edelgard isn't going to look a gift horse in the mouth. She dismisses Hubert, who seems happy to leave.

She and Lysithea are alone again. The pheromones from earlier still hang in the air, but her mind is rapidly clearing. Edelgard wonders what the usual etiquette for afterwards is when something like this happens. The few times she had gone into heat or rut before, Hubert had procured someone suitable and discreet who left as soon as the act was over. 

Edelgard looks at Lysithea's body face down on her bed and wonders if she already fell asleep during her and Hubert's brief exchange. She wouldn't be surprised.

"Mmmph." Lysithea's face presses against the mattress, muffling her voice, but her hand finds Edelgard's sleeve and tugs. Edelgard lets herself be pulled down, closer to Lysithea than she had expected.

"Lysithea?" she asks. Lysithea turns her head away from the mattress, facing Edelgard.

"Can I..." Lysithea yawns. "Can I sleep here for a little bit?" Her hair is strewn over her face. 

"Of course," Edelgard says immediately, hardly needing to think about it. She reaches out and moves a strand of hair from Lysithea's face, uncovering her eyes. 

Lysithea wiggles to be closer to Edelgard, and Edelgard shifts to accomodate her. Trying to figure out a way to comfortably lie together facing each other proves too difficult, so Edelgard turns on her side. Lysithea snuggles comfortably into her back, and then runs her hand over the side of Edelgard's hip. Edelgard can't help but squirm, with how tantalizingly close Lysithea is to her more sensitive areas. When Lysithea slides her hand to cup Edelgard's mound. Edelgard unonsciously bucks her hips up.

"Lysithea," she whines. She doesn't trust herself with more words than that.

Lysithea lazily circles Edelgard's clit with her fingers. Edelgard shifts her legs to allow her better access, and to position herself to grind against Lysithea's cock. Lysithea gently pulls her closer, squeezing her breast with her other hand. Edelgard feels something start to build up inside of her. 

And then Lysithea's hand drops away from Edelgard's clit.

Edelgard twists around, torn between shock and outrage that Lysithea would be such a tease right now, but-- 

Lysithea is asleep. Of course she is. Edelgard can't even be angry at being wound up without release, not when Lysithea looks so cute asleep, her face relaxed and her mouth hanging half open.

The tendrils of sleep tug at Edelgard, too. She decides to let herself rest. Her cunt still throbs with arousal, but she can have Lysithea finish what she started later. Slowly drifitng off to sleep, Edelgard realizes that she's glad it was Lysithea who discovered her secret.

**Author's Note:**

> I guess this is also filling my own kink meme prompt of double alpha lysithea knotting alpha/omega hybrid edelgard? Idk if I should put it on there though lol, because I was the one who made the prompt


End file.
